Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$160.45	4.451%	$167.5916	$167.59	$167.60	$167.60
Purchase #2	$112.44	13.736%	$127.8848	$127.88	$127.90	$127.90
Purchase #3	$7.25	9.599%	$7.9459	$7.95	$7.95	$7.90
Purchase #4	$184.95	13.445%	$209.8165	$209.82	$209.80	$209.80
Purchase #5	$129.77	9.393%	$141.9593	$141.96	$141.95	$142.00
Purchase #6	$38.73	13.364%	$43.9059	$43.91	$43.90	$43.90
Purchase #7	$27.42	13.174%	$31.0323	$31.03	$31.05	$31.00
7 purchase totals =	$661.01		$730.1363	$730.14	$730.15	$730.10